Integrating e^x & 1/x
How do I integrate exponentials and 1/x?
- The integrals involving and are
where is the constant of integration
- For the linear function, where and are constants,
- It follows from the last result that
-
- which can be deduced using Reverse Chain Rule
- With ln, it can be useful to write the constant of integration,, as a logarithm
- using the laws of logarithms, the answer can be written as a single term
- where is a constant
- This is similar to the special case of differentiating when
Worked example
A curve has the gradient function.
Given the exact value of is find an expression for.
To find , we need to integrate the expression for
Rewrite as two separate integrals which can be found individually, and factor out any constants.
Use the two results:
The question states that , so substitute in and equate to the given expression.
Simplify and solve to find
Recall from laws of logarithms that
Rewrite the full expression for
or by combining logs, this could be written as